In the three stages of Goetian Demonology, evocation is the first step.
What you are doing is calling to the spirits, not any particular spirit, but to the spirits in general: trying to contact a spirit, any spirit. While "summoning" is to issue a harsh command, something like "avast" in naval terminology, evocation is more gathering than hunting, tuning into the cosmic shortwave or chatline to see who's there....Mmm? Maybe it's angels, maybe it's souls in Summerland, maybe it's demons, or even a Trickster!
This is how spirit work is done. The Goetia is more of a field guide than a catalogue. Once you learn how to call the birds, these are what the birds are.
Invoking is getting whatever spirit you need for your purposes. And then some...